Jet noise still remains as a major problem in the design of jet engines. Certain experimental and developmental work has led to the conclusion that in turbofan engines having a two nozzle system, noise alleviation can be achieved by utilizing augmentors in the outer fan duct. This produces a velocity profile of the jet exhaust where there is a higher velocity in the outer coannular jet flow, and a lower velocity in the inner portion of the jet flow.
It is an object of the present invention to provide a jet engine with the turbine section and exhaust section so arranged as to produce a jet exhaust velocity profile to alleviate noise generated by the engine.
In a patentability search which was conducted on the concept of the present invention and some other concepts relating to jet engines, a number of United States patents were disclosed. While an examination by the applicant of these various patents indicates that they are not directly relevant to the present invention as prior art, these are cited in this application to insure that the applicant is fully complying with his obligation to disclose to the U.S. Patent and Trademark Office all prior art which might be considered relevant.
U.S. Pat. No. 2,527,732, Imbert, disclosed a turboprop engine where in a lower power mode air is directed away from the turbine. When there is requirement for a rapid increase in power, the bypass air is directed into the turbine to create the additional power in a relatively short period of time.
U.S. Pat. No. 2,630,673, Woll, disclosed a jet engine where air from the compressor is directed through a bypass passageway to provide cooling for a variable area nozzle at the aft end of the engine.
U.S. Pat. No. 3,049,869, Grenoble, directs air from a low-pressure location in the compressor through a bypass passageway to the aft end of the engine. This bypassed air is combined with over-rich exhaust gas to reburn the mixture at a location rearwardly of the turbine in the engine.
U.S. Pat. No. 3,161,018, Sandre, discloses a combined turbojet-ramjet engine where low pressure air is used in conjunction with a bypass turbojet.
U.S. Pat. No. 3,296,800, Keenan et al, shows an arrangement somewhat similar to the Sandre patent noted immediately above.
U.S. Pat. No. 3,514,952, Schumacher et al, discloses a variable bypass turbo-fan engine. During subsonic cruise, the air from the fan is directed through the bypass ducts. During supersonic cruise, valve means close off the bypass ducts so that the air is directed through the compressor and thence to the combustion chamber of the engine.
U.S. Pat. No. 3,520,138, Fox, discloses a plurality of power turbines arranged in series with passageways provided around the second and third turbines, and with valves disposed in the passageways to progressively open or close the passageways. The second and third power turbine combinations are connected to thrust-producing devices for vertical takeoff and landing aircraft or some other desired application.
U.S. Pat. No. 3,641,766, Uehling, discloses an engine arrangement where the thrust output of a gas turbine engine is modulated without the necessity of varying the speed of the engine. This device bypasses a portion of the compressor discharge to a manifold which has a plurality of swirl-inducing nozzles which in turn are able to decrease the delay time between increased thrust demand and actual thrust output while maintaining engine speed.
U.S. Pat. No. 3,879,941, Sargisson, discloses a variable cycle gas turbine engine with a fan having a forward section axially spaced from an aft section. A variable flow bypassing valve is disposed intermediate the forward and aft fan sections in order that air flow between the forward and aft fan sections may be connected either in series flow relationship or in bypassing parallel relation depending upon the desired mode of engine operation. The variable cycle engine also includes a variable flow geometry inlet duct in direct flow connection to the fan for furnishing an inlet airflow to the fan. Within the variable engine cycle is a core engine having a compressor, combuster and turbine in series flow relationship, wherein the compressor receives a portion of the compressed airflow from the fan. A fan turbine section downstream of the core engine is also provided to drive the fan.
U.S. Pat. No. 3,841,091, Sargisson et al, discloses a jet engine which is intended to operate efficiently at both subsonic and supersonic speeds. This embodies a variable cycle tandem propulsion system comprising a forward turbo-fan engine having a fan, gas generator, and power turbine arranged in axially serial flow relation. An independent turbojet engine is co-axially displaced downstream of the turbo-fan engine and includes a compressor, a combuster and turbine also arranged in axially spaced serial flow relation. An outer exhaust duct is provided for directing the exhaust steam from the turbo-fan engine rearward around the turbojet engine. There is also included a variable cross over valve means which may be operated in two modes, e.g., subsonic and supersonic. In the subsonic mode, air flow exiting from the fan which bypasses around the gas generator is directed to the outer exhaust duct means while at the same time a separate inlet ambient air flow stream is directed to the inlet of the turbojet. In its supersonic mode, air flow exiting from the fan which bypasses around the gas generator is directed to the turbojet inlet, thereby supercharging the inlet airflow to the turbojet.
U.S. Pat. No. 3,068,644, Worsham et al, relates primarily to a particular type of nozzle wherein shroud flaps are used to control the configuration of a secondary nozzle through which secondary air is directed.
U.S. Pat. No. 3,769,797, Stevens, discloses an engine configuration where bypass flow of an engine is used for vertical takeoff and landing mode of operation.
U.S. Pat. No. 2,458,600, Imbert et al, shows an arrangement of a turbo-fan engine.
U.S. Pat. No. 2,505,660, Baumann, discloses a thrust "augmentor" comprising in combination at least two coaxial contra-rotationally bladed turbine rotors adapted to be driven by a flow of high velocity combustive gas.
U.S. Pat. No. 3,118,276, Keenen et al, discloses a turbo-fan engine where the fan air communicates with the exhaust gas duct downstream of the turbine or turbines through one or more mixing chutes which extend into the exhaust gas duct.
U.S. Pat. No. 3,316,717, Castle et al, discloses a turbo-fan engine having a variable bypass ratio. This is accomplished by placing fans fore and aft of the gas turbine unit. The fans operate in series for a low bypass ratio, or in parallel for a high bypass ratio.
U.S. Pat. No. 3,903,690, Jones, discloses a turbo-fan engine where all of the bladed stages of the turbine and substantially all of the compressor blades are rotor stages.
U.S. Pat. No. 3,910,375, Hache et al, discloses a jet engine silencer where there is a jet nozzle, and means are provided to inject air into the flow steam emitted from the jet nozzle.
U.S. Pat. No. 3,987,621, Sabatella, Jr. et al, simply discloses a turbo-fan engine where the inner stream includes no noise suppression and the jet exhaust noise generated at take-off is reduced in the outer jet exhaust stream.